Okay, maybe Rosemary Clooney never sang “I’ll Take Menhaden,” but this fish is lately turning our city into islands of joy.

Reports are coming in from the Newtown Creek, Hudson River, and upper East River that menhaden, locally known as pogy and most often bunker fish, are appearing in huge numbers. The video above was posted by Riverkeeper, the most active nongovernmental estuary environmental litigator in our estuary. That’s great news for whales and other sea mammals, as well as bluefish, striped bass, herons, egrets, and other larger fish predators. You’ll see huge swaths of water dance and glint when bunkers breach to escape predators below. Before they’re ever visible, they ride currents into our estuary as eggs and hatch here, to grow from larvae into adult fish.

Bunkers do more than directly sustain these other cherished species as food. For their ability to clean water, these silvery schoolers can be seen as mobile oysters. As “Four Fish” author Paul Greenberg notes, “An adult menhaden can rid four to six gallons of water of algae in a minute.” Much like huge baleen whales, little bunkers are filter feeders. When their numbers plummet, brown algal tides overtake bays, creating dead zones.

Before European colonization, Native Americans ate these fish and used them as fertilizer because their oiliness is both delectable (fishers say you’ll never have to butter a bunker) and a powerful nutrient. Indeed, the words menhaden and pogy derive from Algonquin terms referencing the fertilizing practice.

Sadly, bunker fish haven’t had a good century. they died in masses in the 1980s when bluefish herded them into hypoxic shallows in the the Long Island Sound. They’ve been overfished for 32 of the past 54 years, according to the Atlantic States Marine Fisheries Commission. Commercial operators spot schools by airplane, deploy refrigerated ships to the area, and catch bunkers with nets and, because they school so densely, vacuums. A single fish oil and fish meal company, Omega Protein, is responsible for 90% of the nation’s catch. It’s not active in the NYC region.

Interestingly, what could spare the bunker is what it eats: algae. Companies are starting to farm algae in vats to produce omega-3 fatty acids and other goods for nutritional supplements and livestock feeds. The controlled setting also prevents mercury contamination and other potential pollutants from entering human food systems.